A laser processing system based on inelastic scattering

Abstract

This invention relates to a laser processing system, specifically a laser processing system based on inelastic scattering, addressing the technical problem of reducing the heat-affected zone while achieving high-efficiency laser processing in existing technologies. The laser processing system based on inelastic scattering includes a GHz-level femtosecond optical frequency comb, an inelastic scattering signal detection module, an inelastic scattering signal processing module, and a processing control module. The GHz-level femtosecond optical frequency comb outputs a probe beam and a reference beam. The inelastic scattering signal detection module sets the material to be processed and generates phonons and inelastic scattering signals after the probe beam passes through the material. The inelastic scattering signal processing module combines the reference beam and the inelastic scattering signals to generate an inversion spectrum. The processing control module triggers the GHz-level femtosecond optical frequency comb to output a high-power laser, which, together with phonons on the material that resonate with the laser, completes the processing of the material.

Description

Technical Field

[0001] This invention relates to a laser processing system, and more specifically to a laser processing system based on inelastic scattering. Background Technology

[0002] Lasers, with their small divergence angle and excellent monochromaticity, offer advantages such as non-contact processing, high quality, and high efficiency, making them the preferred choice for processing various materials. The essence of laser processing is that a focused laser beam uses heat conduction to dissolve, vaporize, and plasma-ionize the material being processed, thereby achieving various applications such as cutting, drilling, surface treatment, welding, and surface layer peeling. Currently, both continuous-wave lasers and long-pulse lasers, with pulse widths reaching the femtosecond range, are ultrafast lasers and can be used for laser processing.

[0003] When processing materials using continuous-wave or long-pulse lasers, some of the molten material in the processing area is ejected as high-speed droplets, affecting the surrounding morphology. The remaining unevaporated molten material re-solidifies into irregular shapes in this area, resulting in an uneven processing zone and problems such as slag and microcracks. Unlike these light sources, femtosecond lasers exhibit nonlinear, non-equilibrium, and multi-scale characteristics in their interaction with matter, breaking through the limitations of traditional laser processing and demonstrating their capabilities in high-quality material processing. Due to the advantage of shorter pulses, the thermal diffusion length generated during material processing is much smaller than the laser penetration length. Simultaneously, the high peak power of femtosecond lasers enables rapid ionization of materials, directly transforming them into a mixture of plasma, vapor, and nanodroplets. Therefore, femtosecond laser processing not only reduces damage to surrounding non-processed areas but also improves the cleanliness of the processed area.

[0004] Currently, femtosecond lasers are mostly generated based on the saturable absorption effect. Phase locking is achieved by controlling the allowed modes within the resonant cavity to produce a series of ultrashort pulses with the same envelope. The pulse interval is determined by the length of the resonant cavity. Theoretically, laser pulses with a repetition frequency on the order of GHz can be processed at speeds of 10-1. 9 The repetition rate is times per second, which is unattainable by ultrafast lasers in the kHz or MHz range. In other words, reducing the pulse interval, i.e., increasing the repetition frequency, can significantly improve processing efficiency. However, in existing technologies, repetition frequencies above several hundred kHz lead to heat accumulation and a large heat-affected zone, making them unsuitable for high-precision or high-quality micromachining.

[0005] Therefore, how to reduce the heat-affected zone while ensuring the efficiency of laser processing has become an urgent technical problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problem that existing technologies cannot achieve high-efficiency laser processing while reducing the heat-affected zone, and to provide a laser processing system based on inelastic scattering.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A laser processing system based on inelastic scattering is characterized by comprising a GHz-level femtosecond optical frequency comb, an inelastic scattering signal detection module, an inelastic scattering signal processing module, and a processing control module. The output of the GHz-level femtosecond optical frequency comb is used to output one probe beam and another reference beam. An inelastic scattering signal detection module is placed in the optical path of the probe light. The inelastic scattering signal detection module is used to set the material to be processed and to generate phonons and inelastic scattering signals after the probe light passes through the material to be processed. The inelastic scattering signal processing module is set in the optical path of the reference light and the inelastic scattering signal to superimpose the reference light and the inelastic scattering signal and generate the inversion spectrum of the inelastic scattering signal; The control terminal of the processing control module is connected to the inelastic scattering signal detection module to adjust the position of the material to be processed; the input terminal of the processing control module is connected to the output terminal of the inelastic scattering signal processing module to receive the inversion spectrum; the output terminal of the processing control module is connected to the input terminal of the GHz-level femtosecond optical frequency comb to generate a trigger signal based on the inversion spectrum, triggering the GHz-level femtosecond optical frequency comb to output a probe light, and the comb tooth spacing of the probe light in the frequency domain is an integer multiple of the frequency shift of the inelastic scattering, and the material to be processed is processed using the probe light and the phonons on the surface of the material to be processed.

[0008] Furthermore, the GHz-level femtosecond optical frequency comb includes a GHz-level solid-state femtosecond mode-locked laser, a frequency comb locking unit connected to the GHz-level solid-state femtosecond mode-locked laser, a first photodetector, and a second photodetector; A GHz-level solid-state femtosecond mode-locked laser is used to output probe and reference beams; both probe and reference beams exhibit comb-like spectral lines in the frequency domain. The frequency comb locking unit is connected to the two output terminals of the GHz-level solid-state femtosecond mode-locked laser via a first photodetector and a second photodetector, respectively. The frequency comb locking unit is used to control the comb tooth spacing and single comb tooth frequency of the probe light and the reference light. The first photodetector is used to monitor the comb tooth spacing of the probe light and the reference light, and the second photodetector is used to monitor the single comb tooth frequency of the probe light and the reference light.

[0009] Furthermore, the inelastic scattering signal detection module includes a focusing lens, a spatial light filter, and a reflector arranged sequentially along the detection light path, as well as an angle adjustment frame disposed between the focusing lens and the spatial light filter; Angle adjustment brackets are used to set the material to be processed; A focusing lens is used to focus the probe light onto the material to be processed, and the incident light forms an angle with the surface of the material to be processed; The material to be processed is used to receive incident light and generate phonon and inelastic scattering signals; Spatial light filters are used to filter out incident light; The reflector is used to change the direction of the inelastic scattering signal and direct it to the inelastic scattering signal processing module.

[0010] Furthermore, the inelastic scattering signal processing module includes a right-angle prism arranged sequentially in the optical path of the reference light and the inelastic scattering signal, a photodetector arranged in the optical path of the right-angle prism's output light, a digital-to-analog converter, and a digital signal processor; The photodetector, digital-to-analog converter, and digital signal processor are electrically connected in sequence. A right-angle prism is used to combine the reference light and the inelastic scattered signal to form a beat frequency signal; Photodetectors are used to receive beat frequency signals and convert them into analog electrical signals; A digital-to-analog converter is used to convert analog electrical signals into digital electrical signals; A digital signal processor is used to convert digital electrical signals into inversion spectra and send them to the input of the processing control module.

[0011] Furthermore, the processing control module includes a microprocessor and a switch connected in sequence; The microprocessor's control terminal is electrically connected to the angle adjustment frame via a switch, and its output terminal is electrically connected to the input terminal of a GHz-level solid-state femtosecond mode-locked laser. The microprocessor is used to control the switch to open when the inversion spectrum is strongest, thereby fixing the angle adjustment frame, and sending a command to trigger the GHz-level solid-state femtosecond mode-locked laser to output high-power laser to process the material to be processed.

[0012] Furthermore, the system also includes a single-mode jumper disposed between the GHz-level solid-state femtosecond mode-locked laser and the focusing lens, the single-mode jumper being used to increase the power of the probe light.

[0013] Furthermore, the locking methods of the frequency comb locking unit include repetition frequency locking and carrier envelope offset locking; Alternatively, the locking methods of the frequency comb locking unit include repetition frequency locking and PDH comb tooth locking.

[0014] Furthermore, the angle between the incident light and the surface of the material to be processed is greater than 0° and less than 180°.

[0015] Furthermore, the digital signal processor is a digital signal processor with fast Fourier transform.

[0016] Furthermore, the adjustment range of the comb tooth spacing and the single comb tooth frequency of the probe light and the reference light are both ±5kHz, and the step accuracy is 1Hz.

[0017] The beneficial effects of this invention are: 1. This invention discloses a laser processing system based on inelastic scattering. It uses a highly stable, narrow-linewidth comb spectrum generated by a GHz-level femtosecond optical frequency comb as the processing light source. The inelastic scattering signal obtained by the inelastic scattering signal processing module serves as a feedback signal, which is transmitted to the processing control module. The processing control module then adjusts the angle between the material to be processed and the incident light. When the inverted spectral intensity of the inelastic scattering signal obtained by the inelastic scattering signal processing module significantly increases, the processing control module triggers the GHz-level femtosecond optical frequency comb to output a high-power laser. This laser, along with phonons on the material to be processed that are at the same frequency as the laser, completes the processing of the material. This solves the contradictory problem of high laser processing efficiency and a small heat-affected zone.

[0018] 2. This invention discloses a laser processing system based on inelastic scattering, which effectively improves the processing efficiency of the material to be processed by utilizing inelastic scattering signals. When a laser (i.e., the probe light) is projected onto a non-gain medium (i.e., the material to be processed), inelastic scattering occurs. The loss of the laser by the non-gain medium can be divided into absorption and scattering. When inelastic scattering occurs, atoms / molecules within the non-gain medium oscillate, generating phonons. The frequency of the phonons is the frequency shift of inelastic scattering. When the comb spacing of the probe light generated by the GHz-level femtosecond optical frequency comb in the frequency domain is an integer multiple of the frequency shift of inelastic scattering, the frequency of the laser-induced phonons is exactly an integer multiple of the repetition frequency of the probe light (i.e., the comb spacing). Simultaneously, since the comb spacing is significantly larger than the spectral linewidth of the phonons, sufficient conditions for resonant absorption are met. The rising edge of each pulse of the probe light can overlap with the rising edge of the phonons excited by it, increasing the absorption rate of the laser by the material to be processed by at least one order of magnitude, thus significantly improving the processing efficiency.

[0019] 3. This invention provides a laser processing system based on inelastic scattering, which has the advantage of minimal thermal damage at the processing edges. The GHz-level femtosecond optical frequency comb is composed of a GHz-level solid-state femtosecond mode-locked laser and a frequency comb locking unit. Under the control of the frequency comb locking unit, the comb spectrum in the frequency domain of the GHz-level solid-state femtosecond mode-locked laser exhibits a stable state. Based on the narrow phonon linewidth generated by the stable comb spectrum, the propagation of phonons is confined to the unit cell of the material to be processed. This allows the excited phonons and their carried energy to diffuse freely only within a small area on the surface of the material to be processed, greatly reducing the area of ​​thermal damage. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an embodiment of a laser processing system based on inelastic scattering according to the present invention.

[0021] Explanation of reference numerals in the attached figures: 1-GHz femtosecond optical frequency comb, 11-GHz solid-state femtosecond mode-locked laser, 12-frequency comb locking unit, 2-inelastic scattering signal detection module, 21-focusing lens, 22-material to be processed, 23-angle adjustment frame, 24-spatial light filter, 25-reflector, 3-inelastic scattering signal processing module, 31-right angle prism, 32-photodetector, 33-digital-to-analog converter, 34-digital signal processor, 4-processing control module, 41-microprocessor, 42-switch. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figure 1 As shown, a laser processing system based on inelastic scattering includes a GHz-level femtosecond optical frequency comb 1, an inelastic scattering signal detection module 2, an inelastic scattering signal processing module 3, and a processing control module 4.

[0024] The GHz-level femtosecond optical frequency comb 1 consists of a GHz-level solid-state femtosecond mode-locked laser 11 and a frequency comb locking unit 12. The GHz-level solid-state femtosecond mode-locked laser 11 is used to output probe light and reference light. Both the probe light and the reference light exhibit stable comb-shaped spectra in the frequency domain. The comb tooth spacing of the comb spectrum is 5 GHz. At the same time, under the control of the frequency comb locking unit 12, the adjustment range of the comb tooth spacing and the frequency of a single comb tooth is ±5 kHz, and the step accuracy is 1 Hz.

[0025] The frequency-comb locking unit 12 is connected to the two output terminals of the GHz-level solid-state femtosecond mode-locked laser 11 via a first photodetector and a second photodetector, respectively. The frequency-comb locking unit 12 controls the comb spacing and single comb frequency of the probe and reference beams. The first photodetector monitors the comb spacing of the probe and reference beams, and the second photodetector monitors the single comb frequency of the probe and reference beams. The two output terminals of the GHz-level solid-state femtosecond mode-locked laser 11 are used to output the probe beam and the second output the reference beam.

[0026] The inelastic scattering signal detection module 2 is disposed in the optical path of the probe light, and is used to set the material to be processed 22, so that the probe light generates phonon and inelastic scattering signals after passing through the material to be processed 22. The inelastic scattering signal detection module 2 includes a focusing lens 21, a spatial light filter 24 and a reflector 25 arranged sequentially along the probe light path, and an angle adjustment frame 23 disposed between the focusing lens 21 and the spatial light filter 24. The angle adjustment frame 23 is used to set the material to be processed 22. The focusing lens 21 is used to focus the probe light and incident it onto the material to be processed 22, and the incident light forms an angle with the surface of the material to be processed 22. The material to be processed 22 is used to receive the incident light and generate phonon and inelastic scattering signals. The spatial light filter 24 is used to filter out the incident light. The reflector 25 is used to change the direction of the inelastic scattering signal and incident it onto the inelastic scattering signal processing module 3.

[0027] The inelastic scattering signal processing module 3 is disposed in the optical path of the reference light and the inelastic scattering signal, and is used to superimpose the reference light and the inelastic scattering signal to generate the inversion spectrum of the inelastic scattering signal. The inelastic scattering signal processing module 3 includes a right-angle prism 31 disposed sequentially in the optical path of the reference light and the inelastic scattering signal, a photodetector 32 disposed in the output optical path of the right-angle prism 31, a digital-to-analog converter 33, and a digital signal processor 34; the photodetector 32, the digital-to-analog converter 33, and the digital signal processor 34 are electrically connected in sequence; the right-angle prism 31 is used to superimpose the reference light and the inelastic scattering signal to form a beat frequency signal; the photodetector 32 is used to receive the beat frequency signal and convert it into an analog electrical signal; the digital-to-analog converter 33 is used to convert the analog electrical signal into a digital electrical signal; and the digital signal processor 34 is used to convert the digital electrical signal into an inversion spectrum and send it to the input terminal of the processing control module 4.

[0028] The processing control module 4 includes a microprocessor 41 and a switch 42 connected in sequence. The control terminal of the microprocessor 41 is electrically connected to the angle adjustment frame 23 through the switch 42, and its output terminal is electrically connected to the input terminal of the GHz-level solid-state femtosecond mode-locked laser 11. The microprocessor 41 is used to control the switch 42 to open when the inversion spectrum is strongest, thereby fixing the angle adjustment frame 23, and sending a command to trigger the GHz-level solid-state femtosecond mode-locked laser 11 to output high-power laser to process the material 22 to be processed.

[0029] The first output, serving as the probe light, is incident on the focusing lens 21 via a single-mode jumper. After being focused by the focusing lens 21, it is incident on the surface of the material to be processed 22, forming an angle greater than 0° and less than 180° with the surface of the material to be processed 22. The material to be processed 22 is in close contact with the angle adjustment frame 23. In this embodiment, the output power of each probe light in the frequency domain should reach 1mW to ensure the generation of inelastic scattering signals. The inelastic scattering signal generated by the material to be processed 22 is filtered by the spatial light filter 24 to obtain a high-quality inelastic scattering signal, and then the light path direction is changed by the reflector 25 before being incident on the right-angle prism 31.

[0030] The second output, serving as a reference light, is directly incident on the right-angle prism 31. The right-angle prism 31 ensures that the reference light path and the high-quality inelastic scattering signal are completely overlapped, forming a beat frequency signal. The beat frequency signal is converted into an analog electrical signal by the photodetector 32 and sent to the analog-to-digital converter. The analog-to-digital converter converts the analog electrical signal into a digital electrical signal, which is then transmitted to a digital signal processor with fast Fourier transform capabilities. The inversion spectrum of the inelastic scattering signal is then retrieved.

[0031] Inelastic scattering is a phenomenon caused by nonlinear effects in non-gain media, where incident photons can be converted into scattered photons and phonons with slightly lower energy. When the comb spacing of the reference light output by the GHz-level solid-state femtosecond mode-locked laser 11 is an integer multiple of the frequency shift of the inelastic scattering signal, the frequency of the laser-induced phonons is exactly an integer multiple of the pulse repetition frequency of the probe light. At this point, since the comb spacing is significantly larger than the spectral linewidth of the phonons, sufficient conditions for resonant absorption are formed. The rising edge of each pulse can overlap with the rising edge of the phonons excited by it, increasing the absorption rate of the material to be processed 22 by at least one order of magnitude. At the same time, the phonons generated by the stable comb spectrum formed by the GHz-level solid-state femtosecond mode-locked laser 11 have a narrow linewidth, and the propagation of the phonons is confined within the unit cell of the material to be processed 22. This allows the excited phonons and their carried energy to diffuse freely within a small area on the surface of the material to be processed 22, greatly reducing the thermal damage area.

[0032] Therefore, when the comb line spacing of the output GHz-level solid-state femtosecond mode-locked laser 11 matches the frequency shift of the inelastic scattered light spectrum, the intensity of the inelastic scattered spectrum obtained by the digital signal processor 34 will be significantly enhanced. When the signal intensity of the inverted spectrum is at its maximum, the microprocessor 41 issues a command to lock the angle of the angle adjustment frame 23 and close the switch 42, simultaneously triggering the output laser of the GHz-level solid-state femtosecond mode-locked laser 11 and the phonons on the material to be processed 22 with the same frequency as the laser to process the material again. In this way, laser processing with minimal thermal damage and high efficiency can be achieved.

[0033] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A laser processing system based on inelastic scattering, characterized in that: It includes a GHz-level femtosecond optical frequency comb (1), an inelastic scattering signal detection module (2), an inelastic scattering signal processing module (3), and a processing control module (4); The GHz-level femtosecond optical frequency comb (1) includes a GHz-level solid-state femtosecond mode-locked laser (11), a frequency comb locking unit (12) connected to the GHz-level solid-state femtosecond mode-locked laser (11), a first photodetector, and a second photodetector. The GHz-level solid-state femtosecond mode-locked laser (11) is used to output probe light and reference light; both the probe light and the reference light exhibit comb-shaped spectral lines in the frequency domain. The frequency comb locking unit (12) is connected to the two output terminals of the GHz-level solid-state femtosecond mode-locked laser (11) through the first photodetector and the second photodetector, respectively; the frequency comb locking unit (12) is used to control the comb tooth spacing and single comb tooth frequency of the probe light and the reference light; the first photodetector is used to monitor the comb tooth spacing of the probe light and the reference light, and the second photodetector is used to monitor the single comb tooth frequency of the probe light and the reference light. The inelastic scattering signal detection module (2) is set on the optical path of the detection light. The inelastic scattering signal detection module (2) is used to set the material to be processed (22) and to generate phonons and inelastic scattering signals after the detection light passes through the material to be processed (22). The inelastic scattering signal processing module (3) is set in the optical path of the reference light and the inelastic scattering signal, and is used to overlap the reference light and the inelastic scattering signal and generate the inversion spectrum of the inelastic scattering signal; The control terminal of the processing control module (4) is connected to the inelastic scattering signal detection module (2) to adjust the position of the material to be processed (22); the input terminal of the processing control module (4) is connected to the output terminal of the inelastic scattering signal processing module (3) to receive the inversion spectrum; the output terminal of the processing control module (4) is connected to the input terminal of the GHz-level femtosecond optical frequency comb (1) to generate a trigger signal according to the inversion spectrum, trigger the GHz-level femtosecond optical frequency comb (1) to output the probe light, and the comb tooth spacing of the probe light in the frequency domain is an integer multiple of the frequency shift of the inelastic scattering, and the probe light and the phonons on the surface of the material to be processed (22) are used to process the material to be processed (22).

2. The laser processing system based on inelastic scattering according to claim 1, characterized in that: The inelastic scattering signal detection module (2) includes a focusing lens (21), a spatial light filter (24) and a reflector (25) arranged sequentially along the detection light path, and an angle adjustment frame (23) arranged between the focusing lens (21) and the spatial light filter (24); The angle adjustment frame (23) is used to set the material to be processed (22); The focusing lens (21) is used to focus the probe light and then incident it onto the material to be processed (22), and the incident light forms an angle with the surface of the material to be processed (22); The material to be processed (22) is used to receive incident light and generate phonon and inelastic scattering signals; The spatial light filter (24) is used to filter out incident light; The reflector (25) is used to change the direction of the inelastic scattering signal and incident it onto the inelastic scattering signal processing module (3).

3. The laser processing system based on inelastic scattering according to claim 2, characterized in that: The inelastic scattering signal processing module (3) includes a right-angle prism (31) disposed in the optical path of the reference light and the inelastic scattering signal, a photodetector (32) disposed in the optical path of the right-angle prism (31), a digital-to-analog converter (33) and a digital signal processor (34); The photodetector (32), digital-to-analog converter (33), and digital signal processor (34) are electrically connected in sequence; The right-angle prism (31) is used to combine the reference light and the inelastic scattering signal to form a beat frequency signal; The photodetector (32) is used to receive beat frequency signals and convert them into analog electrical signals; The digital-to-analog converter (33) is used to convert analog electrical signals into digital electrical signals; The digital signal processor (34) is used to convert digital electrical signals into inversion spectra and send them to the input of the processing control module (4).

4. The laser processing system based on inelastic scattering according to claim 3, characterized in that: The processing control module (4) includes a microprocessor (41) and a switch (42) connected in sequence; The control terminal of the microprocessor (41) is electrically connected to the angle adjustment frame (23) via a switch (42), and its output terminal is electrically connected to the input terminal of the GHz-level solid-state femtosecond mode-locked laser (11). The microprocessor (41) is used to control the switch (42) to open when the inversion spectrum is strongest, thereby fixing the angle adjustment frame (23) and sending a command to trigger the GHz-level solid-state femtosecond mode-locked laser (11) to output high-power laser to process the material to be processed (22).

5. A laser processing system based on inelastic scattering according to any one of claims 3 or 4, characterized in that: It also includes a single-mode jumper wire positioned between the GHz-level solid-state femtosecond mode-locked laser (11) and the focusing lens (21).

6. The laser processing system based on inelastic scattering according to claim 5, characterized in that: The locking modes of the frequency comb locking unit (12) include repetition frequency locking and carrier envelope offset locking; Alternatively, the locking method of the frequency comb locking unit (12) may include repetition frequency locking and PDH comb tooth locking.

7. The laser processing system based on inelastic scattering according to claim 6, characterized in that: The angle between the incident light and the surface of the material to be processed (22) is greater than 0° and less than 180°.

8. The laser processing system based on inelastic scattering according to claim 7, characterized in that: The digital signal processor (34) is a digital signal processor with fast Fourier transform.

9. The laser processing system based on inelastic scattering according to claim 8, characterized in that: The adjustment range of the comb spacing and single comb frequency of the probe light and reference light is ±5kHz, and the step accuracy is 1Hz.

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